Method of hydrogenating aldehydes and ketones

ABSTRACT

Methods and systems for the hydrogenation of aldehydes and/or ketones are described herein. The methods and systems incorporate the novel use of a high shear device to promote dispersion and solubility of the hydrogen-containing gas (e.g. H 2  gas) in the aldehydes and/or ketones. The high shear device may allow for lower reaction temperatures and pressures and may also reduce hydrogenation time with existing catalysts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/335,253, filed Dec. 15, 2008, which is adivisional application of U.S. patent application Ser. No. 12/142,419,filed Jun. 19, 2008, which claims the benefit under 35 U.S.C. §119(e) ofU.S. Provisional Patent Application No. 60/946,478, filed Jun. 27, 2007.The disclosure of said applications is hereby incorporated herein byreference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

TECHNICAL FIELD

The invention generally relates to apparatus and methods forhydrogenating aldehydes and/or ketones, and more particularly related tothe acceleration of such reactions by high shear mixing.

BACKGROUND OF THE INVENTION

Aldehydes, ketones and corresponding primary alcohols are generalclasses of organic compounds. There are several methods known in anytextbook of organic chemistry and in patent literature for theconversion of aldehydes to the corresponding primary alcohols, such aschemical reduction methods using alkali or alkaline earth metal-derivedborohydrides or aluminium hydrides and metal catalyzed-hydrogenation.Thus, the conversion of aldehydes and ketones into the correspondingalcohols by catalytic hydrogenation is well known. As such, efforts tooptimize aldehyde and/or ketone hydrogenation have been focused oncatalyst technology. Nickel carrier catalysts or Raney nickel arefrequently used as catalysts for the hydrogenation of aldehydes andketones. The catalyst simultaneously binds the H₂ and the aldehydeand/or ketone and facilitates their union. Platinum group metals,particularly platinum, palladium, rhodium and ruthenium, are examples ofhighly active catalysts. Highly active catalysts operate at lowertemperatures and lower pressures of H₂. Non-precious metal catalysts,especially those based on nickel (such as Raney nickel and Urushibaranickel) have also been developed as economical alternatives but they areoften slower or require higher temperatures. The trade-off is activity(speed of reaction) vs. cost of the catalyst and cost of the apparatusrequired for use of high pressures.

Little attention has been paid with regard to non-chemical methods toaccelerate the hydrogenation of aldehydes and/or ketones. Consequently,there is a need for alternative methods for accelerating thehydrogenation of aldehydes and/or ketones for the production of alcohol.

SUMMARY

Methods and systems for the hydrogenation of aldehydes and/or ketonesare described herein. The methods and systems incorporate the novel useof a high shear device to promote dispersion and solubility of thehydrogen-containing gas (e.g. H₂ gas) in the aldehydes and/or ketones.The high shear device may allow for lower reaction temperatures andpressures and may also reduce hydrogenation time with existingcatalysts. Further advantages and aspects of the disclosed methods andsystem are described below.

In an embodiment, a method of hydrogenating an aldehyde or a ketonecomprises introducing a hydrogen-containing gas into an aldehyde orketone stream to form a gas-liquid stream. The method further comprisesflowing the gas-liquid stream through a high shear device so as to forma dispersion with gas bubbles having a mean diameter less than about 1micron. In addition the method comprises contacting the gas-liquidstream with a catalyst in a reactor to hydrogenate the aldehyde or theketone.

In an embodiment, a system for the hydrogenation of an aldehyde or aketone comprises at least one high shear device configured forhydrogenating an aldehyde, a ketone, or combinations thereof The highshear device comprises a rotor and a stator. The rotor and the statorare separated by a shear gap in the range of from about 0.02 mm to about5 mm. The shear gap is a minimum distance between the rotor and thestator. The high shear device is capable of producing a tip speed of theat least one rotor of greater than about 23 m/s (4,500 ft/min). Inaddition, the system comprises a pump configured for delivering a liquidstream comprising liquid phase to the high shear device.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter that form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand the specific embodiments disclosed may be readily utilized as abasis for modifying or designing other structures for carrying out thesame purposes of the present invention. It should also be realized bythose skilled in the art that such equivalent constructions do notdepart from the spirit and scope of the invention as set forth in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow diagram of a process for the hydrogenation ofan aldehyde or a ketone, according to certain embodiments of theinvention.

FIG. 2 is a longitudinal cross-section view of a multi-stage high sheardevice, as employed in an embodiment of the system of FIG. 1.

DETAILED DESCRIPTION

The disclosed methods and systems for the hydrogenation of aldehydesand/or ketones employ a high shear mechanical device to provide rapidcontact and mixing of the hydrogen-containing gas and aldehydes and/orketones in a controlled environment in the reactor/mixer device. Theterm “hydrogen-containing gas” as used herein includes bothsubstantially pure hydrogen gas as well as gaseous mixtures containinghydrogen. In particular, embodiments of the systems and methods may beused in the production of alcohols from the hydrogenation of aldehydesand/or ketones. Preferably, the method comprises a heterogeneous phasereaction of liquid aldehydes and/or ketones with a hydrogen-containinggas. The high shear device reduces the mass transfer limitations on thereaction and thus increases the overall reaction rate.

Chemical reactions involving liquids, gases and solids rely on time,temperature, and pressure to define the rate of reactions. In caseswhere it is desirable to react two or more raw materials of differentphases (e.g. solid and liquid; liquid and gas; solid, liquid and gas),one of the limiting factors in controlling the rate of reaction involvesthe contact time of the reactants. In the case of heterogeneouslycatalyzed reactions there is the additional rate limiting factor ofhaving the reacted products removed from the surface of the catalyst toenable the catalyst to catalyze further reactants. Contact time for thereactants and/or catalyst is often controlled by mixing which providescontact with two or more reactants involved in a chemical reaction. Areactor assembly that comprises an external high shear device or mixeras described herein makes possible decreased mass transfer limitationsand thereby allows the reaction to more closely approach kineticlimitations. When reaction rates are accelerated, residence times may bedecreased, thereby increasing obtainable throughput. Product yield maybe increased as a result of the high shear system and process.Alternatively, if the product yield of an existing process isacceptable, decreasing the required residence time by incorporation ofsuitable high shear may allow for the use of lower temperatures and/orpressures than conventional processes.

System for Hydrogenation of Aldehydes and Ketones. A high shear aldehydeand/or ketone hydrogenation system will now be described in relation toFIG. 1, which is a process flow diagram of an embodiment of a high shearsystem 100 for the production of alcohols via the hydrogenation ofaldehydes and/or ketones. The basic components of a representativesystem include external high shear device (HSD) 140, vessel 110, andpump 105. As shown in FIG. 1, the high shear device may be locatedexternal to vessel/reactor 110. Each of these components is furtherdescribed in more detail below. Line 121 is connected to pump 105 forintroducing either an aldehyde and/or ketone reactant. Line 113 connectspump 105 to HSD 140, and line 118 connects HSD 140 to vessel 110. Line122 is connected to line 13 for introducing an hydrogen-containing gas.Line 117 is connected to vessel 110 for removal of unreacted aldehydesand/or ketones, and other reaction gases. Additional components orprocess steps may be incorporated between vessel 110 and HSD 140, orahead of pump 105 or HSD 140, if desired. High shear devices (HSD) suchas a high shear device, or high shear mill, are generally divided intoclasses based upon their ability to mix fluids. Mixing is the process ofreducing the size of inhomogeneous species or particles within thefluid. One metric for the degree or thoroughness of mixing is the energydensity per unit volume that the mixing device generates to disrupt thefluid particles. The classes are distinguished based on delivered energydensity. There are three classes of industrial mixers having sufficientenergy density to consistently produce mixtures or emulsions withparticle or bubble sizes in the range of 0 to 50 microns. High shearmechanical devices include homogenizers as well as colloid mills.

Homogenization valve systems are typically classified as high energydevices. Fluid to be processed is pumped under very high pressurethrough a narrow-gap valve into a lower pressure environment. Thepressure gradients across the valve and the resulting turbulence andcavitations act to break-up any particles in the fluid. These valvesystems are most commonly used in milk homogenization and can yieldaverage particle size range from about 0.01 μm to about 1 μm. At theother end of the spectrum are high shear device systems classified aslow energy devices. These systems usually have paddles or fluid rotorsthat turn at high speed in a reservoir of fluid to be processed, whichin many of the more common applications is a food product. These systemsare usually used when average particle, or bubble, sizes of greater than20 microns are acceptable in the processed fluid.

Between low energy—high shear devices and homogenization valve systems,in terms of the mixing energy density delivered to the fluid, arecolloid mills, which are classified as intermediate energy devices. Thetypical colloid mill configuration includes a conical or disk rotor thatis separated from a complementary, liquid-cooled stator by aclosely-controlled rotor-stator gap, which is maybe between 0.025 mm and10.0 mm. Rotors are usually driven by an electric motor through a directdrive or belt mechanism. Many colloid mills, with proper adjustment, canachieve average particle, or bubble, sizes of about 0.01 μm to about 25μm in the processed fluid. These capabilities render colloid millsappropriate for a variety of applications including colloid andoil/water-based emulsion processing such as that required for cosmetics,mayonnaise, silicone/silver amalgam formation, or roofing-tar mixing.

An approximation of energy input into the fluid (kW/L/min) can be madeby measuring the motor energy (kW) and fluid output (L/min). Inembodiments, the energy expenditure of a high shear device is greaterthan 1000 W/m³. In embodiments, the energy expenditure is in the rangeof from about 3000 W/m³ to about 7500 W/m³. The shear rate generated ina high shear device may be greater than 20,000 s⁻¹. In embodiments, theshear rate generated is in the range of from 20,000 s⁻¹ to 100,000 s⁻¹.

Tip speed is the velocity (m/sec) associated with the end of one or morerevolving elements that is transmitting energy to the reactants. Tipspeed, for a rotating element, is the circumferential distance traveledby the tip of the rotor per unit of time, and is generally defined bythe equation V (m/sec)=π·D·n, where V is the tip speed, D is thediameter of the rotor, in meters, and n is the rotational speed of therotor, in revolutions per second. Tip speed is thus a function of therotor diameter and the rotation rate. Also, tip speed may be calculatedby multiplying the circumferential distance transcribed by the rotortip, 2πR, where R is the radius of the rotor (meters, for example) timesthe frequency of revolution (for example revolutions (meters, forexample) times the frequency of revolution (for example revolutions perminute, rpm).

For colloid mills, typical tip speeds are in excess of 23 m/sec (4500ft/min) and can exceed 40 m/sec (7900 ft/min). For the purpose of thepresent disclosure the term ‘high shear’ refers to mechanicalrotor-stator devices, such as mills or mixers, that are capable of tipspeeds in excess of 5 m/sec (1000 ft/min) and require an externalmechanically driven power device to drive energy into the stream ofproducts to be reacted. A high shear device combines high tip speedswith a very small shear gap to produce significant friction on thematerial being processed. Accordingly, a local pressure in the range ofabout 1000 MPa (about 145,000 psi) to about 1050 MPa (152,300 psi) andelevated temperatures at the tip of the shear mixer are produced duringoperation. In certain embodiments, the local pressure is at least about1034 MPa (about 150,000 psi).

Referring now to FIG. 2, there is presented a schematic diagram of ahigh shear device 200. High shear device 200 comprises at least onerotor-stator combination. The rotor-stator combinations may also beknown as generators 220, 230, 240 or stages without limitation. The highshear device 200 comprises at least two generators, and most preferably,the high shear device comprises at least three generators.

The first generator 220 comprises rotor 222 and stator 227. The secondgenerator 230 comprises rotor 223, and stator 228; the third generatorcomprises rotor 224 and stator 229. For each generator 220, 230, 240 therotor is rotatably driven by input 250. The generators 220, 230, 240rotate about axis 260 in rotational direction 265. Stator 227 is fixablycoupled to the high shear device wall 255.

The generators include gaps between the rotor and the stator. The firstgenerator 220 comprises a first gap 225; the second generator 230comprises a second gap 235; and the third generator 240 comprises athird gap 245. The gaps 225, 235, 245 are between about 0.025 mm (0.01in) and 10.0 mm (0.4 in) wide. Alternatively, the process comprisesutilization of a high shear device 200 wherein the gaps 225, 235, 245are between about 0.5 mm (0.02 in) and about 2.5 mm (0.1 in). In certaininstances the gap is maintained at about 1.5 mm (0.06 in).Alternatively, the gaps 225, 235, 245 are different between generators220, 230, 240. In certain instances, the gap 225 for the first generator220 is greater than about the gap 235 for the second generator 230,which is greater than about the gap 245 for the third generator 240.

Additionally, the width of the gaps 225, 235, 245 may comprise a coarse,medium, fine, and super-fine characterization. Rotors 222, 223, and 224and stators 227, 228, and 229 may be toothed designs. Each generator maycomprise two or more sets of rotor-stator teeth, as known in the art.Rotors 222, 223, and 224 may comprise a number of rotor teethcircumferentially spaced about the circumference of each rotor. Stators227, 228, and 229 may comprise a number of stator teethcircumferentially spaced about the circumference of each stator. Therotor and the stator may be of any suitable size. In one embodiment, theinner diameter of the rotor is about 64 mm and the outer diameter of thestator is about 60 mm. In further embodiments, the rotor and stator mayhave alternate diameters in order to alter the tip speed and shearpressures. In certain embodiments, each of three stages is operated witha super-fine generator, comprising a gap of between about 0.025 mm andabout 3 mm. When a feed stream 205 including solid particles is to besent through high shear device 200, the appropriate gap width is firstselected for an appropriate reduction in particle size and increase inparticle surface area. In embodiments, this is beneficial for increasingcatalyst surface area by shearing and dispersing the particles.

High shear device 200 is fed a reaction mixture comprising the feedstream 205. Feed stream 205 comprises an emulsion of the dispersiblephase and the continuous phase. Emulsion refers to a liquefied mixturethat contains two distinguishable substances (or phases) that will notreadily mix and dissolve together. Most emulsions have a continuousphase (or matrix), which holds therein discontinuous droplets, bubbles,and/or particles of the other phase or substance. Emulsions may behighly viscous, such as slurries or pastes, or may be foams, with tinygas bubbles suspended in a liquid. As used herein, the term “emulsion”encompasses continuous phases comprising gas bubbles, continuous phasescomprising particles (e.g., solid catalyst), continuous phasescomprising droplets of a fluid that is substantially insoluble in thecontinuous phase, and combinations thereof.

Feed stream 205 may include a particulate solid catalyst component. Feedstream 205 is pumped through the generators 220, 230, 240, such thatproduct dispersion 210 is formed. In each generator, the rotors 222,223, 224 rotate at high speed relative to the fixed stators 227, 228,229. The rotation of the rotors pumps fluid, such as the feed stream205, between the outer surface of the rotor 222 and the inner surface ofthe stator 227 creating a localized high shear condition. The gaps 225,235, 245 generate high shear forces that process the feed stream 205.The high shear forces between the rotor and stator functions to processthe feed stream 205 to create the product dispersion 210. Each generator220, 230, 240 of the high shear device 200 has interchangeablerotor-stator combinations for producing a narrow distribution of thedesired bubble size, if feedstream 205 comprises a gas, or globule size,if feedstream 205 comprises a liquid, in the product dispersion 210.

The product dispersion 210 of gas particles, or bubbles, in a liquidcomprises an emulsion. In embodiments, the product dispersion 210 maycomprise a dispersion of a previously immiscible or insoluble gas,liquid or solid into the continuous phase. The product dispersion 210has an average gas particle, or bubble, size less than about 1.5 μm;preferably the bubbles are sub-micron in diameter. In certain instances,the average bubble size is in the range from about 1.0 μm to about 0.1μm. Alternatively, the average bubble size is less than about 400 nm(0.4 μm) and most preferably less than about 100 nm (0.1 μm).

The high shear device 200 produces a gas emulsion capable of remainingdispersed at atmospheric pressure for at least about 15 minutes. For thepurpose of this disclosure, an emulsion of gas particles, or bubbles, inthe dispersed phase in product dispersion 210 that are less than 1.5 μmin diameter may comprise a micro-foam. Not to be limited by a specifictheory, it is known in emulsion chemistry that sub-micron particles, orbubbles, dispersed in a liquid undergo movement primarily throughBrownian motion effects. The bubbles in the emulsion of productdispersion 210 created by the high shear device 200 may have greatermobility through boundary layers of solid catalyst particles, therebyfacilitating and accelerating the catalytic reaction through enhancedtransport of reactants.

The rotor is set to rotate at a speed commensurate with the diameter ofthe rotor and the desired tip speed as described hereinabove. Transportresistance is reduced by incorporation of high shear device 200 suchthat the velocity of the reaction is increased by at least about 5%.Alternatively, the high shear device 200 comprises a high shear colloidmill that serves as an accelerated rate reactor (ARR). The acceleratedrate reactor comprises a single stage dispersing chamber. Theaccelerated rate reactor comprises a multiple stage inline dispersercomprising at least 2 stages.

Selection of the high shear device 200 is dependent on throughputrequirements and desired particle or bubble size in the outletdispersion 210. In certain instances, high shear device 200 comprises aDispax Reactor® of IKA® Works, Inc. Wilmington, N.C. and APV NorthAmerica, Inc. Wilmington, Mass. Model DR 2000/4, for example, comprisesa belt drive, 4M generator, PTFE sealing ring, inlet flange 1″ sanitaryclamp, outlet flange ¾″ sanitary clamp, 2 HP power, output speed of 7900rpm, flow capacity (water) approximately 300 l/h to approximately 700l/h (depending on generator), a tip speed of from 9.4 m/s to about 41m/s (about 1850 ft/min to about 8070 ft/min). Several alternative modelsare available having various inlet/outlet connections, horsepower,nominal tip speeds, output rpm, and nominal flow rate.

Without wishing to be limited to a particular theory, it is believedthat the level or degree of high shear mixing is sufficient to increaserates of mass transfer and may also produce localized non-idealconditions that enable reactions to occur that would not otherwise beexpected to occur based on Gibbs free energy predictions. Localized nonideal conditions are believed to occur within the high shear deviceresulting in increased temperatures and pressures with the mostsignificant increase believed to be in localized pressures. The increasein pressures and temperatures within the high shear device areinstantaneous and localized and quickly revert back to bulk or averagesystem conditions once exiting the high shear device. In some cases, thehigh shear device induces cavitation of sufficient intensity todissociate one or more of the reactants into free radicals, which mayintensify a chemical reaction or allow a reaction to take place at lessstringent conditions than might otherwise be required. Cavitation mayalso increase rates of transport processes by producing local turbulenceand liquid micro-circulation (acoustic streaming).

Vessel. Vessel or reactor 110 is any type of vessel in which amultiphase reaction can be propagated to carry out the above-describedconversion reaction(s). For instance, a continuous or semi-continuousstirred tank reactor, or one or more batch reactors may be employed inseries or in parallel. In some applications vessel 110 may be a towerreactor, and in others a tubular reactor or multi-tubular reactor. Acatalyst inlet line 115 may be connected to vessel 110 for receiving acatalyst solution or slurry during operation of the system.

Vessel 110 may include one or more of the following components: stirringsystem, heating and/or cooling capabilities, pressure measurementinstrumentation, temperature measurement instrumentation, one or moreinjection points, and level regulator (not shown), as are known in theart of reaction vessel design. For example, a stirring system mayinclude a motor driven mixer. A heating and/or cooling apparatus maycomprise, for example, a heat exchanger. Alternatively, as much of theconversion reaction may occur within HSD 140 in some embodiments, vessel110 may serve primarily as a storage vessel in some cases. Althoughgenerally less desired, in some applications vessel 110 may be omitted,particularly if multiple high shear devices/reactors are employed inseries, as further described below.

Heat Transfer Devices. In addition to the above-mentionedheating/cooling capabilities of vessel 110, other external or internalheat transfer devices for heating or cooling a process stream are alsocontemplated in variations of the embodiments illustrated in FIG. 1.Some suitable locations for one or more such heat transfer devices arebetween pump 105 and HSD 140, between HSD 140 and vessel 110, andbetween vessel 110 and pump 105 when system 1 is operated in multi-passmode. Some non-limiting examples of such heat transfer devices areshell, tube, plate, and coil heat exchangers, as are known in the art.

Pumps. Pump 105 is configured for either continuous or semi-continuousoperation, and may be any suitable pumping device that is capable ofproviding greater than 2 atm pressure, preferably greater than 3 atmpressure, to allow controlled flow through HSD 140 and system 1. Forexample, a Roper Type 1 gear pump, Roper Pump Company (Commerce Georgia)Dayton Pressure Booster Pump Model 2P372E, Dayton Electric Co (Niles,Ill.) is one suitable pump. Preferably, all contact parts of the pumpcomprise stainless steel. In some embodiments of the system, pump 105 iscapable of pressures greater than about 20 atm. In addition to pump 105,one or more additional, high pressure pump (not shown) may be includedin the system illustrated in FIG. 1. For example, a booster pump, whichmay be similar to pump 105, may be included between HSD 140 and vessel110 for boosting the pressure into vessel 110. As another example, asupplemental feed pump, which may be similar to pump 105, may beincluded for introducing additional reactants or catalyst into vessel110.

Hydrogenation of Aldehydes and Ketones. In operation for the catalytichydrogenation of aldehydes and/or ketones, respectively, a dispersiblehydrogen-containing gas stream is introduced into system 100 via line122, and combined in line 113 with either an aldehyde and/or ketonestream to form a gas-liquid stream. The hydrogen-containing gas may behydrogen, or any other suitable molecular hydrogen-containing gas, ormixture of gases, for example. Alternatively, the hydrogen-containinggas may be fed directly into HSD 140, instead of being combined with theliquid reactant (i.e., aldehyde and/ketone) in line 113. Pump 105 isoperated to pump the liquid reactant (aldehyde and/or ketone) throughline 121, and to build pressure and feed HSD 140, providing a controlledflow throughout high shear device (HSD) 140 and high shear system 100.

In a preferred embodiment, hydrogen gas may continuously be fed into thealdehyde/ketone stream 112 to form a high shear device feed stream (e.g.a gas-liquid stream) in line 113. In high shear device 140, hydrogen gasand the aldehyde and/or ketone are highly dispersed such thatnanobubbles and/or microbubbles of the hydrogen-containing gas areformed for superior dissolution of the hydrogen-containing gas intosolution. Once dispersed, the dispersion may exit high shear device 140at high shear device outlet line 118. Stream 118 may optionally enterfluidized or fixed bed 142 in lieu of a slurry catalyst process.However, in a slurry catalyst embodiment, high shear outlet stream 118may directly enter hydrogenation reactor 110 for hydrogenation. Thereaction stream may be maintained at the specified reaction temperature,using cooling coils in the reactor 110 to maintain reaction temperature.Hydrogenation products (e.g. alcohols) may be withdrawn at productstream 116.

In an exemplary embodiment, the high shear device comprises a commercialdisperser such as IKA® model DR 2000/4, a high shear, three stagedispersing device configured with three rotors in combination withstators, aligned in series. The disperser is used to create thedispersion of hydrogen-containing gas in the liquid medium comprising analdehyde and/or ketone (i.e., “the reactants”). The rotor/stator setsmay be configured as illustrated in FIG. 2, for example. The combinedreactants enter the high shear device via line 113 and enter a firststage rotor/stator combination having circumferentially spaced firststage shear openings. The coarse dispersion exiting the first stageenters the second rotor/stator stage, which has second stage shearopenings. The reduced bubble-size dispersion emerging from the secondstage enters the third stage rotor/stator combination having third stageshear openings. The dispersion exits the high shear device via line 118.In some embodiments, the shear rate increases stepwise longitudinallyalong the direction of the flow. For example, in some embodiments, theshear rate in the first rotor/stator stage is greater than the shearrate in subsequent stage(s). In other embodiments, the shear rate issubstantially constant along the direction of the flow, with the stageor stages being the same. If the high shear device includes a PTFE seal,for example, the seal may be cooled using any suitable technique that isknown in the art. For example, the reactant stream flowing in line 113may be used to cool the seal and in so doing be preheated as desiredprior to entering the high shear device.

The rotor of HSD 140 is set to rotate at a speed commensurate with thediameter of the rotor and the desired tip speed. As described above, thehigh shear device (e.g., colloid mill) has either a fixed clearancebetween the stator and rotor or has adjustable clearance. HSD 140 servesto intimately mix the hydrogen-containing gas and the reactant liquid(i.e., aldehyde and/or ketone). In some embodiments of the process, thetransport resistance of the reactants is reduced by operation of thehigh shear device such that the velocity of the reaction is increased bygreater than a factor of about 5. In some embodiments, the velocity ofthe reaction is increased by at least a factor of 10. In someembodiments, the velocity is increased by a factor in the range of about10 to about 100 fold. In some embodiments, HSD 140 delivers at least 300L/h with a power consumption of 1.5 kW at a nominal tip speed of atleast 4500 ft/min, and which may exceed 7900 ft/min (140 m/sec).Although measurement of instantaneous temperature and pressure at thetip of a rotating shear unit or revolving element in HSD 140 isdifficult, it is estimated that the localized temperature seen by theintimately mixed reactants may be in excess of 500° C. and at pressuresin excess of 500 kg/cm² under high shear conditions. The high shearmixing results in dispersion of the hydrogen-containing gas in micron orsubmicron-sized bubbles. In some embodiments, the resultant dispersionhas an average bubble size less than about 1.5 μm. Accordingly, thedispersion exiting HSD 140 via line 118 comprises micron and/orsubmicron-sized gas bubbles. In some embodiments, the mean bubble sizeis in the range of about 0.4 μm to about 1.5 μm. In some embodiments,the mean bubble size is less than about 400 nm, and may be about 100 nmin some cases. In many embodiments, the microbubble dispersion is ableto remain dispersed at atmospheric pressure for at least 15 minutes.

Once dispersed, the resulting gas/aldehyde, gas/ketone, orgas/ketone/aldehyde dispersion exits HSD 140 via line 118 and feeds intovessel 110, as illustrated in FIG. 1. As a result of the intimate mixingof the reactants prior to entering vessel 110, a significant portion ofthe chemical reaction may take place in HSD 140, with or without thepresence of a catalyst. Hydrogenation may also occur in the HSDresulting in alcohol output from the HSD. This may be driven by thereaction conditions within the HSD. Accordingly, in some embodiments,reactor/vessel 110 may be used primarily for heating and separation ofvolatile reaction products from the alcohol product. Alternatively, oradditionally, vessel 110 may serve as a primary reaction vessel wheremost of the alcohol product is produced. Vessel/reactor 110 may beoperated in either continuous or semi-continuous flow mode, or it may beoperated in batch mode. The contents of vessel 110 may be maintained ata specified reaction temperature using heating and/or coolingcapabilities (e.g., cooling coils) and temperature measurementinstrumentation. Pressure in the vessel may be monitored using suitablepressure measurement instrumentation, and the level of reactants in thevessel may be controlled using a level regulator (not shown), employingtechniques that are known to those of skill in the art. The contents arestirred continuously or semi-continuously.

Commonly known hydrogenation reaction conditions may suitably beemployed as the conditions of the production of an alcohol byhydrogenating the aldehyde and/or the ketone by using the catalysts.There is no particular restriction as to the reaction conditions.However, the hydrogen pressure is selected usually within a range offrom about atmospheric pressure to 100 atm, more preferably from 10 to60 atm, and the reaction temperature may be within a range of from about15° C. to about 350° C., alternatively from about 20° C. to about 220°C.

The hydrogen-containing feed gas supplied to system 100 preferablycontains a major amount of hydrogen and at most a minor amount of one ormore inert gases, such as nitrogen, methane, other low molecular weighthydrocarbons, such as ethane, propane, n-butane and iso-butane, carbonoxides, neon, argon or the like. The hydrogen-containing gas may includeat least about 50 mole % up to about 95 mole % or more (e.g. about 99mole %) of H₂ with the balance comprising one or more of N₂, CO, CO₂,Ar, Ne, CH₄ and other low molecular weight saturated hydrocarbons. Insome cases, e.g. when using nickel catalysts, the presence of CO and CO₂cannot be tolerated and the total carbon oxides concentration in thehydrogen-containing feed gas should not be more than about 5 ppm. Suchhydrogen-containing gases can be obtained in conventional manner fromsynthesis gas and other usual sources of hydrogen-containing gases,followed by appropriate pre-treatment to remove impurities, such assulphurous impurities (e.g. H₂S, COS, CH₃SH, CH₃SCH₃, and CH₃SSCH₃) andhalogen-containing impurities (e.g. HCl and CH₃Cl) which would exert adeleterious influence on catalytic activity, i.e. catalyst inhibition,poisoning or deactivation. Suitable hydrogen-containing gases may beprepared according to usual production techniques. Thus thehydrogen-containing feed gas may be, for example, a 94 mole % hydrogenstream produced by steam reforming of natural gas.

The aldehyde and/or the ketone for the reaction may be used alone or incombination as a mixture of different types. The aldehydes and ketonesto be hydrogenated can have any structure, such as, aliphatic, aromatic,heteroaromatic, aliphatic-aromatic or aliphatic-heteroaromatic. They canalso contain other functional groups, and it should be determinedbeforehand whether these functional groups should remain unchanged orshould be hydrogenated themselves.

Embodiments of the disclosed process may be suitable for hydrogenatingstraight or branched aldehyde(s). The described process may be used forhydrogenating a wide variety of straight or branched chain, saturated orunsaturated aldehydes containing from 2 to 22 carbon atoms. Thesealdehydes include without limitation, saturated aldehydes likeacetaldehyde, propionaldehyde, isobutyraldehyde, n-butyraldehyde,isopentylaldehyde, n-pentyl aldehyde, 2-methyl pentyl aldehyde,crotonaldehyde, 2-ethyl hexaldehyde, methyl pentyl aldehyde, 2-ethylbutyraldehyde, and unsaturated C3-8 aldehydes like acrolein, 2-ethylpropylacrolein, and benzaldehyde, furaldehyde, pyridinylaldehyde and thelike. The aldehyde may be in a substantially pure state or admixed witha component(s) other than an aldehyde. Further, a mixture of aldehydesmay be employed. It is contemplated that an alcohol, an ester for analiphatic hydrocarbon, may be used as a solvent.

The ketone may be any compound having the formula, R₁(C═O)R₂. R₁-R₂ mayindependently comprise an alkyl group, a cyclic group, an aromaticgroup, a heterocyclic group, an alkenyl group, or combinations thereof.R₁-R₂ may be the same or different from one another.

Catalyst. If a catalyst is used to promote the hydrogenation reaction,it may be introduced into the vessel via line 115, as an aqueous ornonaqueous slurry or stream. Alternatively, or additionally, catalystmay be added elsewhere in the system 100. For example, catalyst slurrymay be injected into line 121. In some embodiments, line 121 may containa flowing aldehyde and/or ketone stream and/or aldehyde/ketone recyclestream from vessel 110.

In embodiments, any catalyst suitable for catalyzing a hydrogenationreaction may be employed. An inert gas such as nitrogen may be used tofill reactor 110 and purge it of any air and/or oxygen. Any catalystknown to those of skill in the art may also be utilized forhydrogenation. Suitable catalysts may be any of the catalysts normallyused for hydrogenation of aldehydes and/or ketones. Catalysts such asthese generally comprise one or more transition metals or compounds ofone or more transition metals in a form suitable for hydrogenation.Catalysts comprising one or more metals from group VIII or VIIIA of theperiodic system of elements and/or one or more of their compounds arepreferably used for the process according to the invention. The metalsiron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium andplatinum and compounds thereof have proved to be particularlysuccessful. For economic reasons, and also by virtue of its particularefficiency, nickel or one or more of its compounds is particularlyconveniently used as catalyst for the hydrogenation of aldehydes and/orketones in the disclosed process. These include copper based andplatinum based hydrogenation catalysts. Other examples of suitablecatalysts include without limitation, copper chromite; cobalt compounds;nickel; nickel compounds which may contain small amounts of chromium orother promoters; mixtures of copper and nickel and/or chromium; and amixture of reduced copper oxide-zinc oxide. Embodiments of the processmay employ any of the described catalysts.

In an embodiment, the catalyst may be a ruthenium catalyst. Theruthenium catalyst of the present invention can be obtained by reducingthe alkali metal ruthenate with a reducing agent selected from the groupconsisting of methanol, formaldehyde and formic acid. It is preferablysupported on a carrier. There is no particular restriction as to thecarrier to be used. It may be active carbon, alumina or silica. However,it is preferred to use active carbon as the carrier, particularly forthe production of a highly active catalyst. For the preparation of acarrier-supported catalyst, an aqueous solution or an aqueous alkalinesolution of an alkali metal ruthenate is first impregnated within acarrier.

Embodiments may utilize catalysts in which the catalytically activemetallic ruthenium is precipitated in finely divided form onto suitablecarrier materials such as aluminum oxide, titanium dioxide, kieselguhr,silica gel, molecular sieves, and zeolites of natural or syntheticorigin. Catalysts whose carrier material consists of activated carbonare preferred. According to the invention, these carrier catalysts areemployed as finely divided powders as before, but in compacted lumpyform. Catalyst may be fed into reactor 110 through catalyst feed stream115.

The bulk or global operating temperature of the reactants is desirablymaintained below their flash points. In some embodiments, the operatingconditions of system 100 comprise a temperature in the range of fromabout 50° C. to about 300° C. In specific embodiments, the reactiontemperature in vessel 110, in particular, is in the range of from about90° C. to about 220° C. In some embodiments, the reaction pressure invessel 110 is in the range of from about 5 atm to about 50 atm.

The dispersion may be further processed prior to entering vessel 110 (asindicated by arrow 18), if desired. In vessel 110, aldehyde and/orketone hydrogenation occurs via catalytic hydrogenation. The contents ofthe vessel are stirred continuously or semi-continuously, thetemperature of the reactants is controlled (e.g., using a heatexchanger), and the fluid level inside vessel 110 is regulated usingstandard techniques. Aldehyde and/or ketone hydrogenation may occureither continuously, semi-continuously or batch wise, as desired for aparticular application. Any reaction gas that is produced exits reactor110 via gas line 117. This gas stream may comprise unreacted aldehydesand/or ketones, and hydrogen-containing gas, for example. Preferably thereactants are selected so that the gas stream comprises less than about6% hydrogen-containing gas by weight. In some embodiments, the reactiongas stream in line 117 comprises from about 1% to about 4%hydrogen-containing gas by weight. The reaction gas removed via line 117may be further treated, and the components may be recycled, as desired.

The reaction product stream including unconverted aldehydes and/orketones and corresponding byproducts exits vessel 110 by way of line116. The alcohol product may be recovered and treated as known to thoseof skill in the art.

Multiple Pass Operation. In the embodiment shown in FIG. 1, the systemis configured for single pass operation, wherein the output from vessel110 goes directly to further processing for recovery of alcohol product.In some embodiments it may be desirable to pass the contents of vessel110, or a liquid fraction containing unreacted aldehyde and/or ketone,through HSD 140 during a second pass. In this case, line 116 isconnected to line 121 via dotted line 120, and the recycle stream fromvessel 110 is pumped by pump 105 into line 113 and thence into HSD 140.Additional hydrogen-containing gas may be injected via line 122 intoline 113, or it may be added directly into the high shear device (notshown).

Multiple High shear devices. In some embodiments, two or more high sheardevices like HSD 140, or configured differently, are aligned in series,and are used to further enhance the reaction. Their operation may be ineither batch or continuous mode. In some instances in which a singlepass or “once through” process is desired, the use of multiple highshear devices in series may also be advantageous. In some embodimentswhere multiple high shear devices are operated in series, vessel 110 maybe omitted. In some embodiments, multiple high shear devices 140 areoperated in parallel, and the outlet dispersions therefrom areintroduced into one or more vessel 110.

While embodiments of the invention have been shown and described,modifications thereof can be made by one skilled in the art withoutdeparting from the spirit and teachings of the invention. Theembodiments described herein are exemplary only, and are not intended tobe limiting. Many variations and modifications of the inventiondisclosed herein are possible and are within the scope of the invention.Where numerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations. Use of broader terms such as comprises, includes,having, etc. should be understood to provide support for narrower termssuch as consisting of, consisting essentially of, comprisedsubstantially of, and the like. Accordingly, the scope of protection isnot limited by the description set out above but is only limited by theclaims which follow, that scope including all equivalents of the subjectmatter of the claims. Each and every original claim is incorporated intothe specification as an embodiment of the invention. Thus, the claimsare a further description and are an addition to the preferredembodiments of the present invention. The disclosures of all patents,patent applications, and publications cited herein are herebyincorporated by reference, to the extent they provide exemplary,procedural or other details supplementary to those set forth herein.

1. A method of hydrogenating an aldehyde or a ketone comprising: a)introducing a gas stream comprising hydrogen into a high shear device;b) introducing a liquid stream comprising an aldehyde or ketone intosaid high shear device; c) forming a dispersion in said high sheardevice comprising gas bubbles having a mean diameter of less than about1 micron; and d) contacting the dispersion with a catalyst in a reactorto hydrogenate the aldehyde or the ketone.
 2. The method of claim 1,wherein the gas bubbles have an average diameter of less than about 400nm.
 3. The method of claim 1, wherein the gas bubbles have an averagediameter of no more than about 100 nm.
 4. The method of claim 1, whereinthe liquid stream includes a liquid-gas stream formed by mixing analdehyde- or ketone-containing stream with a second hydrogen-containinggas stream.
 5. The method of claim 1, wherein (c) comprises subjectingsaid gas and liquid to high shear mixing at a tip speed of at leastabout 23 m/sec.
 6. The method of claim 5, wherein said high shear mixingproduces a local pressure of at least about 1000 MPa at said tip.
 7. Themethod of claim 1, wherein (c) comprises subjecting said gas and liquidto a shear rate of greater than about 20,000 s⁻¹.
 8. The method of claim1, wherein forming said dispersion comprises an energy expenditure of atleast about 1000 W/m³.
 9. The method of claim 1, wherein said high sheardevice increases the reaction rate of said hydrogenation by at least 5times.
 10. The method of claim 1 further comprising contacting thedispersion with a hydrogenation catalyst to form an alcohol.
 11. Themethod of claim 1, wherein said reactor is a fixed bed reactorcomprising the catalyst.
 12. The method of claim 1, wherein the catalystis selected from the group consisting of copper, zinc, iron, ruthenium,osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, andcombinations thereof.
 13. The method of claim 1 comprising mixing thecatalyst with the liquid stream to form a slurry before (b).
 14. Themethod of claim 1, wherein (d) results in the production of an alcohol.15. The method of claim 1, wherein said high shear device comprises arotor and a stator separated by a shear gap in the range of from about0.02 mm to about 5 mm, wherein the shear gap is a minimum distancebetween said rotor and said stator.
 16. The method of claim 1, whereinthe high shear device comprises two or more rotors and two or morestators.
 17. The method of claim 1, wherein said high shear devicecomprises a rotor tip and said device is configured for operating at aflow rate of at least 300 L/h at a tip speed of at least about 23 m/sec.18. The method of claim 1 further comprising utilizing at least two highshear devices.
 19. The method of claim 1, wherein the high shear deviceis capable of producing a dispersion of hydrogen gas bubbles having amean diameter of less than about 5 μm in the liquid.
 20. The method ofclaim 1, wherein the high shear device comprises a high shear millhaving a tip speed of greater than about 5 m/s (1000 ft/min).